NEW YORK (BLOOMBERG) - Tim Leissner was supposed to be the US government's star witness in the bribery case against Roger Ng, the only Goldman Sachs Group banker to go to trial in the multibillion-dollar 1MDB scandal. Instead, crucial evidence regarding Leissner could end up tanking the case, after the US disclosed that it failed to turn over to the defence more than 15,500 documents related to him.

On Wednesday (Feb 23), the judge said she would pause the trial to give the defence time to review the newly disclosed evidence, which the government says it discovered on Tuesday night.

In a hearing outside the jury's presence, Ng's lawyer Marc Agnifilo told the court he may ask for a mistrial.

"In the middle of the night, we got a letter from the government describing by its own admission an 'inexcusable' discovery disclosure," an angry Agnifilo told US District Judge Margo Brodie in federal court in Brooklyn, New York.

He added that he had complained for at least two and a half years about the government's "slow-walking" evidence he needs to defend his client.

"The government absolutely did not live up to its obligation," Agnifilo said. "This is a categorically serious failure. This is unforgivable."

In a letter filed with the court, prosecutors had admitted they failed to share the evidence related to Leissner, who was Ng's boss at Goldman.

Leissner is crucial to the government's argument Ng conspired with him, while Ng's lawyers said on Wednesday that the documents support their argument that Ng played no role in the scheme.

The error "is inexcusable," prosecutor Alixandra Smith said in the letter.

US$35m payment

Agnifilo said some of the evidence he has reviewed rebuts the government's claims that Leissner, who has pleaded guilty and is cooperating with prosecutors, paid Ng a US$35 million (S$47 million) kickback for his role in the 1MDB scandal. Agnifilo said the evidence supports the defence theory that the money was a transfer from Leissner's wife to Ng's wife for a separate business transaction.

He told the judge he is considering making a request for a mistrial and even asking Brodie to grant a dismissal of the indictment and all criminal charges against Ng.

Brodie said she would pause the trial after Leissner finishes his direct testimony so the defence can catch up before its cross-examination.

Wednesday's disclosure comes after prosecutors in Manhattan federal court were dressed down two years ago for their failure to turn over evidence in a case involving sanctions. US District Judge Alison Nathan issued a blistering opinion in September 2020 stating there were "serious and pervasive issues" involving disclosure and misleading statements by the government attorneys. She called for an investigation and required that every prosecutor in that office read her decision.